To improve temporal resolution in axial cardiac scans, short scans (e.g., half-scans, partial scans, etc.) are often used to obtain enough image data to allow a full representation of a segment of the heart to be reconstructed. Short scans involve taking x-ray measurements about a portion, but less than the entire circumference of the heart about an axis of rotation. Since short scans require less time to complete than full, 360° scans for a given scan speed, there is a greater likelihood of completing a short scan between heartbeats, a period when the heart is relatively stationary. A cross-sectional tomographic image, or “slice,” of the heart is reconstructed from the data collected as a result of the x-ray measurements. However, heartrates naturally vary, even while a patient is resting. Because the duration of time between heartbeats is not constant, triggering a short scan so the short scan can be completed during a time when the heart is relatively stationary is difficult.
Modern CT scanners have the capability to capture x-ray data for single slices that are sixteen (16 cm) centimeters in axial length, which allows reconstruction of an image of the entire heart from a single short scan. But most cardiac CT scans continue to be performed with CT scanners that have a collimation requiring four individual slices, each four (4 cm) centimeters in axial length, to be assembled into an image of the entire heart. A portion of the data for one or more of the slices may be acquired during a time when motion of the heart during the cardiac cycle is most pronounced. The use of data acquired during the pronounced motion of the heart results in distortions to the resulting tomographic image referred to as motion artifacts. Motion artifacts appearing in one or more of the slices to be assembled into the image of the entire heart diminish the quality of the assembled image.